The objective of the proposed research is to discover ways by which drugs can be employed to regulate or alter the release of oxytocin from the neurohypophysis. It is hoped that these studies will provide a basis for developing drugs useful for treatment of problems associated with lactation, labor, and especially premature labor. The dopaminergic regulation of oxytocin and neurophysin release will be assessed in vitro using the isolated hypothalamo-neurohypophysial system of rats. The effects of dopaminergic agonists and antagonists on gestation time, labor, and lactation will be examined. Oxytocin will be measured by bioassay, radioimmunoassay, and by high pressure liquid chromatography of the fluorescamine derivative of the hormone. The turn-over of oxytocin (and vasopressin) will be determined using labeled amino acid precursors in animals receiving dopaminergic drugs and during various physiological states. The possible release of oxytocin from a fetal source will be examined by measuring the oxytocin content of pituitary glands of fetal and newborn pups. Experiments are proposed for studying possible sex differences in the metabolism of oxytocin by the kidney. The study of an oxytocin derivative is also proposed.